The unmanned X-37B orbital vehicle, which resembles a mini space shuttle, was launched atop an Atlas V rocket Wednesday at 1:03 EST, Universe Today reported.
As wit previous missions, the Air Force has declined to discuss any details of the spacecraft's equipment or what the goal of the current mission may be.
United Launch Alliance, in charge of the launch, provided a web cast of the blastoff but ended the streaming video ,"at the request of our customer [the Air Force]," when the X-37B arrived in orbit.
Launched like a satellite inside the nose fairing of the Atlas V, the space plane can operate for extended periods in low Earth orbit before returning to land on a runway in the same manner as NASA's full-size space shuttles.
The possible missions and payloads of the "mini shuttle" -- about a quarter the size of a NASA space shuttle -- have been the subject of much speculation, with suggestions of Earth observations, surveillance, or deploying military satellites.
The launch, originally set for October, was delayed several times by problems with the Atlas V rocket.